Various vehicle systems may consume vehicle power when a vehicle is powered off (e.g., during ignition OFF). Some of these devices are at least partially controlled by a vehicle user such as the entertainment system and interior and exterior vehicle lighting. Other devices may consume power in a manner which is more transparent to the user's awareness such as a vehicle's global positioning satellite (GPS) device or a vehicle telematics device. Typically, such devices draw current from power stored in a vehicle battery when the vehicle is powered down.
It is known to power down some of these devices during at least part of the ignition OFF duration. For example, in vehicles having a telematics unit for placing and receiving voice and data calls, it is known to enter into a standby mode after the vehicle is switched off, wherein the telematics unit is powered down and then periodically powered back up briefly to see if there are any call attempts being made to the telematics unit. This process may be referred to as discontinuous reception (DRx). While useful for lessening power draw on the vehicle batteries, such approaches are not typically initiated until hours or days after the vehicle is powered down. This helps insure that any operator-controlled use of the telematics unit or other system has ceased.